going blower is different than going turbo
^that

Switching from one boost method to another (generally, and assuming the same boost level) keeps a few things, such as:
1. intake manifold (probably)
2. ignition (but not the actual advance or curve)
3. oil system (except as needed for turbo supply/drain)
4. rods, pistons including CR (no, everyone doesn't agree)
5. crank
6. main caps
7. block
8. head bolts/stud quality

But a few things will definitely change:
1. cam duration, split, lobe height
2. head flow
3. in/ex flow bias
4. the entire exhaust system, including primary tube diameter
5. rocker in/ex bias
6. stall speed

There will also be differences between centrifugal (Vortech, Pro Charger) and positive (GMC, Kobelco, Autorotor, Sprintex), especially stall speed